The depletion of fossil fuel and their polluting effect has spurred interest in renewable sources of energy, e.g., solar energy, wind energy, tidal energy, draught animal power, and energy that can be derived from plant sources.
Reference is made to a review article titled “Biodiesel fuel production by transesterification of oils” by H. Fukuda et al. (Journal of Bioscience and Bioengineering, vol. 92, No. 5, (2001), 405-416) that discusses the drawbacks of using vegetable oils directly in place of fossil diesel and the three approaches being investigated to overcome these drawbacks, namely, pyrolysis, micro-emulsification and transesterification. This article further states that transesterification is the preferred approach, and that such transesterification of oils can be effected by three routes, namely, acid catalysis, base catalysis and enzyme catalysis. While each route has its merits, base catalysis is the most industrially acceptable route presently in view of the much faster rate of reaction and inexpensive nature of the catalyst. The drawbacks of the current alkali-catalysed process as reported are: higher than ambient reaction temperature (60-70° C.), problems encountered with free fatty acid in the raw oil, difficulty encountered in recovering glycerol and methanol, and need for repeated washing of the methyl ester with water to effect its purification. No mention is made about the fate of the catalyst and the manner of effluent disposal.
Reference is made to the same review article above wherein it is stated that in a report entitled “An overview of biodiesel and petroleum diesel life cycles” by Sheehan et al. (Report of National Renewable Energy Laboratory (NREL) and US-Department of Energy (DOE) Task No. BF886002, May (1998)), it has been shown that the benefit of using biodiesel is proportionate to the level of blending with petroleum diesel. The overall life cycle emissions of CO2 from 100% biodiesel fuel are 78.45% lower than those of petroleum diesel, and a blend with 20% biodiesel fuel reduces net CO2 emissions by 15.66%.
Reference is made to the article entitled “Biodiesel: A Renewable Energy Fuel” by N. S. K. Prasad (Chemical Weekly, Aug. 17, 2004, p 183-188) wherein it is mentioned on p 186 that: “Biodiesel is widely used in Europe. Germany has more than 1500 filling stations selling biodiesel at the pump. France is the world's largest producer. All French Diesel fuel contains between 2-5% biodiesel that will soon apply to the whole of Europe. In the 1990s, France launched the local production of biodiesel fuel (known locally as diester) obtained by the transesterification of rape seed oil. It is mixed to the proportion of 5% into regular diesel fuel, and to the proportion of 30% into the diesel fuel used by captive fleets (public transportation). Renault, Peugeot and other manufacturers have certified truck engines for use with up to this partial biodiesel. Experiments with 50% biodiesel are underway.”
Reference is made to a Google search:
http://www.google.co.in/search?hl=en&q=Biodiesel+preparation&btnG=Google+Search&meta, that yielded 13,200 different results related to biodiesel preparation.
Reference is made to the paper entitled “Integrated biodiesel production: a comparison of different homogeneous catalysts systems” by Vicente et al. (Bioresource Technology 92 (2004) 297-305) wherein the process of transesterification of vegetable oils with different base catalysts is described. The authors report that the maximum yield of biodiesel obtained by them using alkali catalysed methanolysis is ca. 85.32% and 90.54% for NaOH and KOH-catalysed reactions, respectively, for laboratory scale experiments with oil having <0.5% FFA. Besides less than desirable yield, other drawbacks of the process are the need to carry out the transesterification reaction at higher than ambient conditions and the lack of any suitable solution to the problem of catalyst disposal and effluent management.
U.S. Pat. No. 6,489,496, describes a process for transesterification of triglycerides with continuous removal of glycerol produced during the reaction using centrifugal separator to enhance the reaction rate. The major draw back of the process is that the transesterification reaction is carried out at 70° C. The process does not describe the removal of catalyst from the glycerol, removal of methanol from the ester product, and recycling the excess ethanol; and hence the process is rendered uneconomical for industrial practice.
U.S. Pat. No. 6,712,867 discloses a process for production of fatty acid methyl esters from fatty acid triglycerides wherein the process of transesterification of triglycerides using methanol and/or ethanol, alkali catalyst and cosolvent like ether. The major drawbacks of the process are: (i) the use of cosolvent, higher than ambient transesterification temperature, and lack of any attempt to deal with the problem of spent catalyst discharge.
The Internet site http://www.svlele.com/biodiesel_in_india, discloses a detailed project report on Biodiesel manufacturing unit of 10 kl per day capacity. The project report is based on known prior art which, as mentioned above, has important limitations.
US Patent Application No. 20030229238 dated Dec. 11, 2003 relates to a continuous transesterification process, wherein the process includes a continuous, plug-flow environment with a single-pass residence time as low as about 10 seconds, and a conversion of at least 70 percent. The major draw back of the process is that it employs high temperature and pressure for transesterification reaction.
In another article W. Zhou et al, titled “Ethyl esters from the Single-Phase Base-Catalyzed Ethanolysis of Vegetable Oils” (JAOCS vol. 80, 367-371, 2003) the base catalyzed transesterification of vegetable oils has been carried out using co-solvent tetrahydrofuran (THF) and ethanol at elevated temperature. The draw backs of this publication are: the transesterification is carried out at elevated temperatures, and the use of additional solvent in the system renders the process complicated and expensive. Further, the article is silent on the recovery of the catalyst in any form and that of excess alcohol used in the reaction.
There are several literature reports wherein lipases have been used as catalysts in industrial processes for producing Biodiesel; for example Bradin (U.S. Pat. No. 6,398,707) uses a pretreated immobilized lipase to catalyze the transesterification or esterification. Further, the pretreated immobilized lipase is prepared by immersing an immobilized lipase in an alcohol having a carbon atom number not less than 3 and the pretreatment of lipase requires time up to 48 hours. Such processes are time consuming for industrial production. In another article published by Watanabe, et al., [“Continuous Production of Biodiesel Fuel from Vegetable Oil Using Immobilized Candida antarctica Lipase”, JAOCS, vol. 77, pp. 355-360, 2000], there are three major difficulties in using lipase to produce Biodiesel. The first difficulty is that price of lipase is much higher than price of alkali. Secondly lipase process requires up to 48 hours to complete the reaction which is significantly longer than with base catalysis. The third difficulty is that the activity of lipase is relatively low, and it requires pretreatment with an alcohol having a carbon atom number not less than 3. Another difficulty with enzyme catalysis not alluded to in the article is that, for transesterification with methanol which is the preferred alcohol for biodiesel preparation, the reaction is extremely sluggish and proceeds in most cases with only low conversion efficiency, if at all.
Although ways of circumventing the problems associated with alkali-catalysed biodiesel preparation through use of alternative catalysts such as enzymes, acids and heterogeneous catalysts are described, it would be greatly beneficial if the base-catalysed process itself could be improved to overcome the current drawbacks. One such reported improvement is 2-stage transesterification but, here again, this slows down the overall throughput of the reaction and it would be desirable if high quality biodiesel, such as that conforming to EN14214 specifications, can be produced in a single stage. There are also no reports of any suitable means of overcoming the problem of messy work up of the crude fatty acid methyl ester obtained on transesterification of triglyceride with methanol, and losses of product/reagents in aqueous effluent. Moreover, given that biodiesel is about promoting green technology, it would be highly desirable if the entire process of producing such biodiesel from raw oil is carried out under ambient conditions. Another limitation of the prior art is that in attempting to maximize biodiesel yield, the process sometimes can be more complex than desirable and it would be of interest to have a simpler process where useful co-products are obtained along with biodiesel and, in the process, the overall method of production is maintained as simple as possible.
A Google search:
http://www.google.co.in/search?hl=en&q=Biodiesel+preparation+from+Jatropba+oil&btnG=Google+Search&meta provided 141 results related to biodiesel from Jatropha curcas oil. The oil obtained from the non-traditional Jatropha curcas plant is non-edible.
Reference is made to a book titled Biofuels and Industrial Products from Jatropha curcas, G. M. Gublitz, M. Mittelbach, M. Trabi, Eds. (1997), wherein it is reported by G. D. Sharma et al. that the J. curcas plant can be grown over a wide range of arid or semi-arid climatic conditions, is hardy to weather conditions, easy to propagate by seed or cuttings, and not browsed by goat or cattle. Reference is also be made to an article by B. Schmook and L. Serralta-Peraza in the same book wherein the authors state that “Taking into account the climatic and edaphic conditions of the Yucatan Peninsula, which are not very favorable for modern agriculture, J. curcas could be an option.” It will be evident that the plant is suitable for cultivation on wasteland and large quantities of biodiesel may become available from wasteland in future if biodiesel of desired quality can be produced in simple and cost-effective manner. Reference is also be made to articles in the above book by E. Zamora et al. and M. N. Eisa on transesterification of J. curcas oil. The articles do not disclose much of the details of the process adopted. Reference is also made to the same book above wherein the utility of Jatropha oil cake, soap cake and glycerol have been reported in different chapters.
Reference is made to the Petroleum Conservation Research Association web site (http://www.pcra.org/petroleum16.html) wherein it is stated that triglycerides, including Jatropha oil, are “readily transesterified in the presence of alkaline catalyst (Lye) at atmospheric pressure and temperature of approximately 60-70° C. with an excess of methanol The mixture at the end of reaction is allowed to settle. The excess methanol is recovered by distillation and sent to a rectifying column for purification and recycled. The lower glycerol layer is drawn off while the upper methyl ester layer is washed with water to remove entrained glycerol Methyl esters of fatty acids are termed as bio-diesel.” Apart from the fact that transesterification is conducted at higher than ambient temperature, no mention is made of the layer from which methanol is recovered or what is done with the alkali. There is also no mention of the complications expected to be encountered when water is added into the crude biodiesel layer.
The Minutes of Meeting of Adhoc Panel of experts of PCD 3 constituted by Bureau of Indian Standards for finalising Specifications of Biodiesel held on 17 Jun. 2004 which has been circulated for comments, wherein it is stated that: “On bio-diesel there are two important overseas standards, namely, EN 14214 and ASTM D 6751. The scope of EN 14214 covers the requirements of bio-diesel for its use as 100% and also for blending with diesel whereas the scope of ASTMD 6751 covers the requirements of bio-diesel only blend stocks.” The report further states that: “Considering the fact that the bio-diesel in India is expected to be manufactured from non edible vegetable oils, members felt that it would be extremely difficult to meet the EN specifications.”
Reference is made to an article by M. N. Eisa, titled “Production of ethyl esters as diesel fuel substitutes in the developing countries” (pp 110-112), in Proceedings on Biofuels and Industrial Products from Jatropha curcas, 23-27 Feb. 1997, held in Managua, Nicaragua. The article discloses the preparation of ethyl ester of oil by base catalyzed transesterification. The draw backs of this process are that they use large excess of ethyl alcohol (up to 70 parts per 100 parts of oil) and they did not recover the catalyst and the reaction temperature is also at around 70° C.
Reference is also be made to a publication by N. Foidl et al, titled “Jatropha Curcas L as a Source For The Production of Biofuel in Nicaragua” (Bioresource Technology, 58, 1996, pp 77-82) wherein it is stated that for developing countries like Nicaragua, Jatropha curcas is a very promising energy plant since the plant can be grown on very poor soils and gives a high average yield of seeds. The publication further describes the method of producing methyl ester of the oil, effectively by the 2-step base-catalysed transesterification process. The oil having 0.60-1.27% FFA is expelled from the seed kernel of Jatropha curcas seeds and then processed with 1.5 equivalents of MeOH and 1.3% KOH in a continuous reactor, with recycling of 90-93% of the methyl ester with fresh oil. The remaining ester phase is mixed with 5% of warm water and then centrifuged to eliminate excess methanol, remaining soaps and glycerol. The main disadvantages of the process are: (i) the need to decorticate the seeds, (ii) the low throughput because of high recycle ratio, and (iii) the high phosphorous (17.5 ppm) and moisture (0.16%) levels which would make the product unsuitable for use as neat biodiesel. No mention is also made of the complications of work up of the crude methyl ester, effluent management and the fate of the catalyst used.
Reference is made to the composition of the oil from J. Curcas seeds of Caboverde variety and Nicaragua variety reported in the above article. It is stated that the oil contains 290 ppm of phosphorous, and its level in biodiesel can be reduced to 17.5 ppm in the adopted process but degumming is necessary to produce biodiesel with <10 ppm of phosphorous as mandated in the EN14214 specifications for B100 biodiesel.
It will be evident from the prior art that there is no report wherein pure biodiesel of EN14214 specification has been prepared from Jatropha curcas oil, not to mention preparation of such premium quality biodiesel from oil expelled directly from whole seeds. Moreover, there is no report of biodiesel preparation under ambient conditions of processing which would minimize generation of greenhouse gases during processing. There is also little indication in the prior art of the economics of production and any attempts to value add effluents and flue gases. Lack of a suitable solution to the problem of spent alkali catalyst value addition, coupled with the cost of catalyst, may compel lower than optimum quantities of catalyst to be otherwise used that can adversely affect the process. There is also no report wherein the process has been optimized keeping the value of all products in mind.
Reference may be made to H. Scherzberg et al. who in their paper entitled ‘Messo pilots new potassium sulphate process’, (Phosphorous & Potassium, 178, March-April 1992, p-20) describe the utility of potassium sulphate as a superior fertilizer having both potassium and sulphur as plant nutrients and additionally having low chloride index.
Reference is made to an article on Potassium Compounds by H. Schultz et al. in Ullmann's Encyclopedia, 6th Edition, 2002, wherein the preparation of potassium carbonate from caustic potash and carbon dioxide is reported to be the most popular. It is further stated that: “the glass industry is the most important consumer of K2CO3. Large amounts are also required for potassium silicate manufacture.” Besides many other applications, potassium carbonate is used as a fertilizer for acidic soil.
Reference is made to U.S. Pat. No. 6,174,501, by H. Noureddini discloses a system and process for producing biodiesel fuel with reduced viscosity and a cloud point below thirty-two (32) degrees Fahrenheit in which the utility of crude glycerol for preparation of glycerol ethers. These ethers are shown to lower the cloud point of the biodiesel obtained through based catalysed transesterification of triglycerides.